Acoustic wave device, method of fabricating the same, filter, and multiplexer

Abstract

An acoustic wave device includes: a piezoelectric substrate; and a pair of comb-shaped electrodes located on the piezoelectric substrate, each of the comb-shaped electrodes being formed mainly of a monocrystalline metal film, each of the comb-shaped electrodes including electrode fingers.

What is claimed is: 
     
       1. An acoustic wave device comprising:
 a piezoelectric substrate; 
 a pair of comb-shaped electrodes located on the piezoelectric substrate, each of the comb-shaped electrodes being formed mainly of a monocrystalline metal film, each of the comb-shaped electrodes including electrode fingers, and 
 an amorphous layer that is in contact with the monocrystalline metal film and the piezoelectric substrate and is located between the monocrystalline metal film and the piezoelectric substrate, the amorphous layer containing, as a main component, a constituent element of at least one of the monocrystalline metal film and the piezoelectric substrate. 
 
     
     
       2. The acoustic wave device according to  claim 1 , wherein
 a direction normal to a surface on which the pair of comb-shaped electrodes is located of the piezoelectric substrate differs from a crystal axis orientation of the monocrystalline metal film. 
 
     
     
       3. The acoustic wave device according to  claim 1 , wherein
 a surface on which the pair of comb-shaped electrodes is located of the piezoelectric substrate differs from a (001) plane when the monocrystalline metal film has a body-centered cubic lattice crystal structure or a face-centered cubic lattice crystal structure, and differs from a (0001) plane when the monocrystalline metal film has a hexagonal close-packed crystal structure. 
 
     
     
       4. A filter comprising:
 the acoustic wave device according to  claim 1 . 
 
     
     
       5. A multiplexer comprising:
 the filter according to  claim 4 . 
 
     
     
       6. An acoustic wave device comprising:
 a piezoelectric substrate; 
 a pair of comb-shaped electrodes located on the piezoelectric substrate, each of the comb-shaped electrodes being formed mainly of a monocrystalline metal film each of the comb-shaped electrodes including electrode fingers, and 
 a bonding film that is in contact with the monocrystalline metal film and the piezoelectric substrate and is located between the monocrystalline metal film and the piezoelectric substrate, the bonding film containing, as a main component, an element different from a constituent element of the monocrystalline metal film and a constituent element of the piezoelectric substrate. 
 
     
     
       7. A filter comprising:
 the acoustic wave device according to  claim 6 . 
 
     
     
       8. A multiplexer comprising:
 the filter according to  claim 7 . 
 
     
     
       9. An acoustic wave device comprising:
 a piezoelectric substrate; 
 a pair of comb-shaped electrodes located on the piezoelectric substrate, each of the comb-shaped electrodes being formed mainly of a monocrystalline metal film, each of the comb-shaped electrodes including electrode fingers, wherein 
 the monocrystalline metal film is made of a metal having a melting point equal to or greater than a melting point of platinum. 
 
     
     
       10. A filter comprising:
 the acoustic wave device according to  claim 9 . 
 
     
     
       11. A multiplexer comprising:
 the filter according to  claim 10 .